An optical element configured using an optically transparent substrate is typically provided with an antireflection film to reduce the reflected light of the incident light.
For example, in the case of a plastic lens for spectacles or the like, the following advantages can be achieved by providing the antireflection film. For example, by controlling the reflectance of incident light coming from a direction perpendicular to the substrate, the transmittance of the light coming from the perpendicular direction can be increased. Further, by preventing reflection of the lens surface facing the eye, user's feeling of flicker caused by the reflection can be inhibited.
A problem with the antireflection film is that the reflection characteristics thereof vary depending on the incident angle of light incident on the optical element. The optical element such as a spectacle lens, a display panel of a display or the like has higher probability to be looked from an oblique direction than from the front. Generally, by controlling the reflectance of the light coming from the perpendicular direction, flicker when seeing from the oblique direction can be substantially inhibited.
However, since the optical element and optical equipment with the optical element incorporated therein have been provided with various high functions, there is a need to not only more reduce the reflectance of the light coming from the perpendicular direction, but also reduce the reflectance of the light coming from the oblique direction. To satisfy such need, an art is proposed in which, by reducing the reflectance of the entire antireflection film as much as possible, the reflectance of light incident coming from the oblique direction is also reduced (see, for example, Patent Document 1)